Melvyn Weiss, the co-founder of now-defunct Milberg, Weiss, Bershad, Hynes & Lerach, died in his sleep on Feb. 2 at the age of 82, his son's law firm, Seeger Weiss announced on Friday.

Weiss was a giant of the plaintiffs bar, from his spectacular success as a class action pioneer to his 30-month federal prison sentence for illegally paying named plaintiffs.

He had been diagnosed with ALS in June, and “lived his last days in the warm company of friends and family, who loved and respected him deeply,” Seeger Weiss said.

Weiss was born in the Bronx in 1935, and worked his way through law school as an accountant.

In 1965, he and Lawrence Milberg launched what at its height was the largest plaintiffs firm in the country, with more than 200 lawyers. Weiss, who was based in New York, was king of East Coast operations, while Bill Lerach presided over the West.

Here's how The American Lawyer in 2007 described Weiss' vision:

“In the 1960s Weiss was one of a handful of attorneys who explored the commercial applications of new amendments to federal rules of procedures, which allowed for expanded class actions. Weiss distinguished himself by aggressively growing the business. 'He was willing to throw a lot money at the cases and take them further [than anyone else],' says Fred Isquith, a class action attorney at Wolf Haldenstein Adler Freeman & Herz. “He was prepared to build a bigger firm. Others were more … risk-averse.'

“Weiss created a lucrative practice for himself and others. Throughout the 1980s and 1990s, Milberg Weiss was to securities class actions what Wachtell, Lipton, Rosen & Katz was to M&A. The passage of the Private Securities Litigation Reform Act in 1995—legislation designed to curb the suits—hardly made a dent.”

Fortune magazine called it “America's meanest law firm,” writing that Milberg Weiss “transformed the humble securities class-action lawsuit into a deadly weapon” and recovered $45 billion for its clients.

And then, it all fell apart.

“The securities class-action law firm of Milberg Weiss Bershad & Schulman was charged today with several criminal counts, including obstructing justice, perjury, bribery and fraud.

“The 20-count indictment, handed up by a federal grand jury in Los Angeles, represents the most prominent confrontation between the government and a law firm in years.”

Weiss pleaded guilty to one count of racketeering conspiracy and served about 18 months of his sentence at a federal prison in Morgantown, West Virginia, followed by time in a halfway house and home confinement. He also paid a $250,000 fine and forfeited $9.7 million.

Lerach got two years, David Bershad and Steven Schulman were both sentenced to six months. The firm, renamed Milberg, paid $75 million to settle federal charges. In January, it combined with Sanders Phillips Grossman, a national mass torts and personal injury firm, and is now known as Milberg Tadler Phillips Grossman.

But even in his heyday, Weiss also believed in giving back. Working pro bono, he represented Holocaust victims against Swiss and German banks and industrial complexes, and victims of the September 11 tragedy. In the early 1990s, he and his wife established the Melvyn and Barbara Weiss Public Interest Foundation at the New York University School of Law, “encouraging generations of lawyers to take on lower-paying public-interest jobs by paying their student loans,” according to Seeger Weiss.

Benjamin Brafman of Brafman & Associates, who represented Weiss in his criminal case, said in an email, “Mel Weiss was perhaps one of the greatest lawyers of this generation and despite the legal difficulties he faced, his brilliant work on behalf of Holocaust survivors is a magnificent part of his legacy, devoting more than 20 years of his life fighting for reparations and ultimately succeeding on an unprecedented level. He was a great friend who will be missed.”

Seeger Weiss name partner Christopher Seeger added, “Mel was a visionary, who was the first to use the class action mechanism to serve as a check against the power and abuses of corporate America to the benefit of millions of individuals in the United States and worldwide,” he said. “To me and many others who had the privilege of working with him, he'll always be remembered as a kind and generous man and a pioneering giant in our field. He truly made this world a better place for the little guy.”